React-本机IOS/Android模拟器问题

Question

我目前正在使用react native构建我的第一个应用程序。当我试图同时为IOS和Android运行模拟器时，我遇到了错误。当我尝试使用"npm run IOS"为IOS运行模拟器时，它成功地运行了模拟器，但当我尝试在App.js中进行更改时，它们不会出现在模拟器菜单中。。。我试着重新启动模拟器好几次，但都没用，我也不能在模拟器中使用命令，比如"cmd+R"来重新加载，即使没有错误消息。当谈到Android时，我甚至不能运行模拟器(使用"npm run Android"(，我总是遇到以下错误消息：

npm ERR！代码ELIFECYCLE npm ERR！errno 1 npm ERR！feedIt@0.0.1安卓：react-native run-androidnpm错误！退出状态1 npm ERR！npm ERR！在处失败feedIt@0.0.1android脚本。npm ERR！这是可能不是npm的问题。可能还有其他日志记录输出。

npm ERR！此运行的完整日志可在以下位置找到：npm ERR
/Users/maurice/.npm/_logs/2020-07-13T08_19_29_328Z-debug.logMaurices MacBook Air：myApp maurice$

这是我的App.js:

/**  * Sample React Native App  *
https://github.com/facebook/react-native  *  * @format  * @flow
strict-local  */
import 'react-native-gesture-handler';
import 'react-native-gesture-handler';
import * as React from 'react';
import {NavigationContainer} from '@react-navigation/native';
const App = () => {
return (
<NavigationContainer>{/* Rest of your app code */}</NavigationContainer>
);
};
export default App;
import React from 'react';
import {
SafeAreaView,
StyleSheet,
ScrollView,
View,
Text,
StatusBar,
} from 'react-native';
import {
Header,
LearnMoreLinks,
Colors,
DebugInstructions,
ReloadInstructions,
} from 'react-native/Libraries/NewAppScreen';
const App: () => React$Node = () => {
return (
<>
<StatusBar barStyle="dark-content" />
<SafeAreaView>
<ScrollView
contentInsetAdjustmentBehavior="automatic"
style={styles.scrollView}>
<Header />
{global.HermesInternal == null ? null : (
<View style={styles.engine}>
<Text style={styles.footer}>Engine: Hermes</Text>
</View>
)}
<View style={styles.body}>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>Step One</Text>
<Text style={styles.sectionDescription}>
Edit <Text style={styles.highlight}>App.js</Text> to change this
screen and then come back to see your edits.
</Text>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>See Your Changes</Text>
<Text style={styles.sectionDescription}>
<ReloadInstructions />
</Text>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>Debug</Text>
<Text style={styles.sectionDescription}>
<DebugInstructions />
</Text>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>Learn More</Text>
<Text style={styles.sectionDescription}>
Read the docs to discover what to do next!
</Text>
</View>
<LearnMoreLinks />
</View>
</ScrollView>
</SafeAreaView>
</>
);
};
const styles = StyleSheet.create({
scrollView: {
backgroundColor: Colors.lighter,
},
engine: {
position: 'absolute',
right: 0,
},
body: {
backgroundColor: Colors.white,
},
sectionContainer: {
marginTop: 32,
paddingHorizontal: 24,
},
sectionTitle: {
fontSize: 24,
fontWeight: '600',
color: Colors.black,
},
sectionDescription: {
marginTop: 8,
fontSize: 18,
fontWeight: '400',
color: Colors.dark,
},
highlight: {
fontWeight: '700',
},
footer: {
color: Colors.dark,
fontSize: 12,
fontWeight: '600',
padding: 4,
paddingRight: 12,
textAlign: 'right',
},
});
export default App;

我无法解决这个问题，希望得到任何帮助。当做Maurice

Answer 1

将代码更改为：

import 'react-native-gesture-handler';
import {NavigationContainer} from '@react-navigation/native';
import React from 'react';
import {
SafeAreaView,
StyleSheet,
ScrollView,
View,
Text,
StatusBar,
} from 'react-native';
import {
Header,
LearnMoreLinks,
Colors,
DebugInstructions,
ReloadInstructions,
} from 'react-native/Libraries/NewAppScreen';
const App: () => React$Node = () => {
return (
<>
<StatusBar barStyle="dark-content" />
<SafeAreaView>
<ScrollView
contentInsetAdjustmentBehavior="automatic"
style={styles.scrollView}>
<Header />
{global.HermesInternal == null ? null : (
<View style={styles.engine}>
<Text style={styles.footer}>Engine: Hermes</Text>
</View>
)}
<View style={styles.body}>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>Step One</Text>
<Text style={styles.sectionDescription}>
Edit <Text style={styles.highlight}>App.js</Text> to change this
screen and then come back to see your edits.
</Text>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>See Your Changes</Text>
<Text style={styles.sectionDescription}>
<ReloadInstructions />
</Text>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>Debug</Text>
<Text style={styles.sectionDescription}>
<DebugInstructions />
</Text>
</View>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>Learn More</Text>
<Text style={styles.sectionDescription}>
Read the docs to discover what to do next!
</Text>
</View>
<LearnMoreLinks />
</View>
</ScrollView>
</SafeAreaView>
</>
);
};
const styles = StyleSheet.create({
scrollView: {
backgroundColor: Colors.lighter,
},
engine: {
position: 'absolute',
right: 0,
},
body: {
backgroundColor: Colors.white,
},
sectionContainer: {
marginTop: 32,
paddingHorizontal: 24,
},
sectionTitle: {
fontSize: 24,
fontWeight: '600',
color: Colors.black,
},
sectionDescription: {
marginTop: 8,
fontSize: 18,
fontWeight: '400',
color: Colors.dark,
},
highlight: {
fontWeight: '700',
},
footer: {
color: Colors.dark,
fontSize: 12,
fontWeight: '600',
padding: 4,
paddingRight: 12,
textAlign: 'right',
},
});
export default App;

您已经定义了两次App组件。你也有一些重复/矛盾的进口。